Actuator joint with non-straight edge

ABSTRACT

A suspension is described. The suspension includes a base plate and a load beam coupled to the base plate. The base plate includes a distal elongated element and a proximal elongated element. The distal elongated element includes at least one non-straight baseplate edge and the proximal elongated element includes at least one non-straight baseplate edge. The load beam includes a first mounting shelf and a second mounting shelf. The load beam is coupled to the base plate such that the first mounting shelf is exposed adjacent to the distal elongated element, and the second mounting shelf is exposed adjacent to the proximal elongated element. The first and second mounting shelves are configured to receive an actuator, such that an edge of the actuator and the at least one non-straight baseplate edge forms a gap.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/025,788 filed on Mar. 15, 2020, which is hereby incorporated byreference in its entirety.

FIELD

This disclosure relates to the field of suspensions for hard diskdrives. More particularly, this disclosure relates to the field ofactuator joints on an actuated suspension configured to provide enhancedstiffness.

BACKGROUND

In a dynamic rigid disk storage device, a rotating disk is employed tostore information. Rigid disk storage devices typically include a frameto provide attachment points and orientation for other components, and aspindle motor mounted to the frame for rotating the disk. A read/writehead is formed on a “head slider” for writing and reading data to andfrom the disk surface. The head slider is supported and properlyoriented in relationship to the disk by a head suspension that providesboth the force and compliance necessary for proper head slideroperation. As the disk in the storage device rotates beneath the headslider and head suspension, the air above the disk also rotates, thuscreating an air bearing which acts with an aerodynamic design of thehead slider to create a lift force on the head slider. The lift force iscounteracted by a spring force of the head suspension, thus positioningthe head slider at a desired height and alignment above the disk whichis referred to as the “fly height.”

Head suspensions for rigid disk drives include a load beam and aflexure. The load beam typically includes a mounting region for mountingthe head suspension to an actuator of the disk drive, a rigid region,and a spring region between the mounting region and the rigid region.The spring region provides a spring force to counteract the aerodynamiclift force generated on the head slider during the drive operation asdescribed above. The flexure typically includes a gimbal region having aslider mounting surface where the head slider is mounted. The gimbalregion is resiliently moveable with respect to the remainder of theflexure in response to the aerodynamic forces generated by the airbearing. The gimbal region permits the head slider to move in pitch androll directions and to follow disk surface fluctuations.

In some examples, the flexure is formed as a separate piece having aload beam mounting region which is rigidly mounted to the distal end ofthe load beam using conventional methods such as spot welds. Headsuspensions of this type typically include a load point dimple formed ineither the load beam or the gimbal region of the flexure. The load pointdimple transfers portions of the load generated by the spring region ofthe load beam, or gram load, to the flexure, provides clearance betweenthe flexure and the load beam, and functions as a point about which thehead slider can gimbal in pitch and roll directions to followfluctuations in the disk surface.

Disk drive manufacturers continue to develop smaller yet higher storagecapacity drives. Storage capacity increases are achieved in part byincreasing the density of the information tracks on the disks (i.e., byusing narrower and/or more closely spaced tracks). As track densityincreases, however, it becomes increasingly difficult for the motor andservo control system to quickly and accurately position the read/writehead over the desired track. Attempts to improve this situation haveincluded the provision of a another or secondary actuator or actuators,such as a piezoelectric, electrostatic or electromagnetic actuator orfine tracking motor, mounted on the head suspension itself. These typesof actuators are also known as second-stage microactuation devices andmay be located at the base plate, the load beam or on the flexure.

Some of these attempts to improve tracking and head slider positioningcontrol have included locating the actuator at the head slider itself.Typically, this type of actuator is sandwiched between the head sliderand the head slider mounting surface of the flexure or other suspensioncomponent or is otherwise directly coupled to the head slider. Movementof the actuator then generally results in relatively direct movement ofthe head slider to provide the desired fine motion of the read/writehead over the tracks of the disk drive.

One problem with this type of set up is shock robustness, especially inthe piezoelectric configurations. In these configurations, the amount ofshock able to be withstood is limited by the fracture limit of thepiezoelectric material because much of the shock load passes through thepiezoelectric element. Making the piezoelectric element thicker, wideror shorter will increase the shock robustness by increasing thestiffness of the element, but these changes will also result in adecrease in the amount of stroke provided by the element. Increases inshock robustness without losing stroke capability would be advantageous.

SUMMARY

A suspension is described. The suspension includes a base plate and aload beam coupled to the base plate. The base plate includes a distalelongated element and a proximal elongated element. The distal elongatedelement includes at least one non-straight baseplate edge and theproximal elongated element includes at least one non-straight baseplateedge. The load beam includes a first mounting shelf and a secondmounting shelf. The load beam is coupled to the base plate such that thefirst mounting shelf is exposed adjacent to the distal elongatedelement, and the second mounting shelf is exposed adjacent to theproximal elongated element. The first and second mounting shelves areconfigured to receive an actuator, such that an edge of the actuator andthe at least one non-straight baseplate edge forms a gap.

In some examples of the suspension, the gap is filled with a firstadhesive, the first adhesive is either a non-conductive adhesive or aconductive adhesive. The non-straight baseplate edge enables enhancedtolerance for placement of the actuator and dispensing of the firstadhesive. Either of the non-straight baseplate edges can include atleast one straight base plate edge portion and at least one concaveportion.

A base plate device is also provided. The base plate device includes adistal elongated element including at least one non-straight baseplateedge. The base plate device also includes a proximal elongated elementseparated by the distal elongated element by an actuator receivingspace. In some examples, the proximal elongated element includes atleast one non-straight baseplate edge.

In some examples of the base plate device, the non-straight baseplateedge can be configured to account for placement capability of theactuator and dispensing capability of the first adhesive. Either of thenon-straight baseplate edges can include at least one straight baseplate edge portion and at least one concave portion.

A suspension device is also provided. The suspension device includes agimbal assembly. The gimbal assembly includes an actuator mounted on thesuspension device with a fixed end and a hinge end, opposite the fixedend. The gimbal assembly also includes a first electrode on a topsurface of the actuator. A second electrode is located on a bottomsurface of the actuator. The second electrode is coupled to a conductivelayer on the suspension device via conductive adhesive. The gimbalassembly also includes a metal base layer located at the hinge end. Themetal base layer includes a non-straight metal layer edge configured tocreate a gap between an edge of the actuator and the metal layer. Thegap is configured to receive non-conductive adhesive to reduce thepossibility of and or prevent an electrical short between the conductiveadhesive and the metal base layer.

In some examples of the suspension, the non-straight edge of the metalbase layer includes at least one straight edge portion and at least oneconcave portion. The conductive layer can be a copper layer. The metalbase layer includes a stainless-steel layer.

A gimbal assembly is also provided. The gimbal assembly includes anactuator mounted on the suspension device with a fixed end and a hingeend, opposite the fixed end. The gimbal assembly also includes a firstelectrode on a top surface of the actuator. A second electrode islocated on a bottom surface of the actuator. The second electrode iscoupled to a conductive layer on the suspension device via conductiveadhesive. The gimbal assembly also includes a metal base layer locatedat the hinge end. The metal base layer includes a non-straight metallayer edge configured to create a gap between an edge of the actuatorand the metal layer. The gap is configured to receive non-conductiveadhesive to reduce the possibility of an electrical short between theconductive adhesive and the metal base layer.

In some examples of the gimbal assembly, the non-straight edge of themetal base layer includes at least one straight edge portion and atleast one concave portion.

While multiple examples are disclosed, still other examples of thepresent disclosure will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative examples of this disclosure. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top perspective view of a prior art magnetic disk driveunit.

FIG. 2 is a top plan view of the suspension of the disk drive of FIG. 1.

FIG. 3 illustrates an actuator joint of a suspension, according to anexample of this disclosure.

FIG. 4 illustrates an actuator joint of FIG. 3 without the actuator,according to an example of this disclosure.

FIG. 5A illustrates an actuator joint of a suspension, according to anexample of this disclosure.

FIG. 5B illustrates the actuator joint of FIG. 5A without the actuator,according to an example of this disclosure.

FIG. 6 illustrates gimbal of a suspension, according to an example ofthis disclosure.

FIG. 7 is cross-sectional view of the actuator area of FIG. 6 takenalong section line B-B′.

DETAILED DESCRIPTION

FIG. 1 is a top perspective view of a magnetic disk drive unit 100. Thedisk drive unit 100 includes a spinning magnetic disk 101, whichcontains a pattern of magnetic ones and zeroes on it that constitutesthe data stored on the disk drive. The magnetic disk 101 is driven by adrive motor. The disk drive unit 100 further includes a suspension 105to which a magnetic head slider is mounted proximate the distal end ofload beam 107. The “proximal” end of a suspension or load beam is theend that is supported, i.e., the end nearest to a base plate which isswaged or otherwise mounted to an actuator arm. The “distal” end of asuspension or load beam is the end that is opposite the proximal end,i.e., the “distal” end is the cantilevered end.

The suspension 105 is coupled to an actuator arm 103, which in turn iscoupled to a voice coil motor 110. The voice coil motor 110 isconfigured to move the suspension 105 arcuately in order to position thehead slider over the correct data track on the magnetic disk 101. Thehead slider is carried on a gimbal (not shown), which allows the sliderto pitch and roll so that it follows the proper data track on thespinning magnetic disk 101, allowing for such variations withoutdegraded performance. Such variations typically include vibrations ofthe disk, inertial events such as bumping, and irregularities in thedisk's surface.

FIG. 2 is a top plan view of a suspension 105 in FIG. 1. The suspension105 can include a base plate 12, and a load beam 107. The load beam 107includes a trace gimbal 152. The trace gimbal 152 can include mountedactuators and a gimbal assembly (not shown). The actuators are operableto act directly on the gimbaled area of the suspension 105 that holdsthe read/write head slider.

The base plate 12 can include at least one actuator joint 17 configuredto receive an actuator 14. The base plate 12 illustrates two actuatorjoints 17, located on opposing sides of the base plate 12. Each actuatorjoint 17 includes actuator mounting shelves 18, formed within load beam107. For example, the actuator mounting shelves 18 can extend from theload beam 107 in a unibody configuration.

Each actuator 14 spans the respective gap in the actuator joint 17. Theactuators 14 are affixed to the mounting shelves 18 by an adhesive. Theadhesive can include conductive or non-conductive epoxy 16 strategicallyapplied at each end of the actuators. The positive and negativeelectrical connections can be made from the actuators 14 to thesuspension's 105 flexible wiring trace and/or to the plate by a varietyof techniques. When the actuator 14 is activated, it expands orcontracts producing fine movements of the read/write head that ismounted at the distal end of suspension 105 thereby changing the lengthof the gap between the mounting shelves 18.

The suspension 105 can be configured as a single-stage actuationsuspension, a dual-stage actuation device, or a tri-stage actuationdevice. Conceivably, any variation of actuators can be incorporated ontothe suspension 105 for the purposes of the examples disclosed herein. Inother words, the suspension 105 may include more or less components thanthose shown without departing from the scope of the present disclosure.The components shown, however, are sufficient to disclose anillustrative example for practicing the disclosed principles.

FIG. 3 illustrates an actuator joint 117 of a suspension 205, accordingto an example of this disclosure. The suspension 205 includes a baseplate 112 and a load beam 107. The load beam 107 can include mountingshelves 118. The base plate 112 can include two extending sections withopposing base plate edges 111. The mounting shelves 118 can be exposedbetween base plate edges 111 such that the distance between opposingedges of the mounting shelves 118 is narrower than the distance betweenthe base plate edges 111. The actuator joint 117 is positioned betweenthe base plate 112 and the load beam 107. The actuator 114 is receivedat the actuator joint 117 between two base plate edges 111 and restingon mounting shelves 118 of the load beam 107. The actuator 114 isseparated from one of the two base plate edges 111 by a gap 102. Thedimension of the gap 102 is configured to account for variousmanufacturing factors, such as, for example actuator 114 placementcapability, adhesive 116 dispensing capability, and other manufacturingtolerances. In some manufacturing processes, the adhesive 116 is firstdispensed on the mounting shelves 118 before the actuator 114 ispositioned and placed within the actuator joint 117.

The dimension of the gap 102 between the actuator 114 and one of the twobase plate edges 111 is also configured to account for the stiffness ofthe actuator joint 117. It has been determined, a smaller gap 102 andthus an actuator 114 with a larger cross section is preferred in orderto enhance the stiffness of the suspension 205, due to the reduction inadhesive. FIG. 4 illustrates the actuator joint 117 without theactuator. Table 1 provides example gaps with varying dimensions and theassociated suspension performance.

TABLE 1 Gap stroke (nm/V) Sway freq. (kHz)  50 um 12.4 21.6 100 um 11.420.8

Table 1 illustrates nominal gap dimensions, which are generally limitedto manufacturing capability, such as adhesive dispensing and spreadcontrol. Gaps with small dimensions (<100 um) increases the chance ofadhesive 116 overflow towards the load beam 107 opening as shown in FIG.3. The present disclosure illustrates additional examples of actuatorjoints configured to reduce the chance of adhesive 116 overflow, whileproviding enhanced stiffness.

FIG. 5A illustrates an actuator joint 317 of a suspension 305, accordingto an example of this disclosure. The suspension 305 includes a baseplate 312 and a load beam 307. The base plate 312 includes a distalelongated element 312A and a proximal elongated element 312B. The distalelongated element 312A and the proximal elongated element 312B can beseparated by an actuator receiving space 312C. The load beam 307includes mounting shelves 318, a first mounting shelf 318A is coupled tothe distal elongated element 312A and a second mounting shelf 318B iscoupled to the proximal elongated element 312B. An actuator 314 isreceived at the actuator joint 317 between the distal elongated element312A and the proximal elongated element 312B of the base plate 312 andresting on the mounting shelves 318 of the load beam 307.

The actuator joint 317 is formed between the distal elongated element312A and the proximal elongated element 312B of the base plate 312 andthe mounting shelves 318 of the load beam 307. The distal elongatedelement 312A of the base plate 312 can be configured with a non-straightbaseplate edge 311 for the actuator joint 317.

The proximal elongated element 312B is also configured with anon-straight baseplate edge 311. For example a non-straight edgeincludes one or more non-straight elements, such as, for example,concave portions, convex portions, sloped portions, warped portions, ora portion incongruent with another section of the edge. A concave edgeportion 315 is illustrated herein as centrally located along thenon-straight baseplate edge 311. The concave edge portion 315 can bedimensionally configured to reduce adhesive 316 overflow. Furthermore,the actuator joint 317 can be configured such that the non-straightbaseplate edge 311 includes at least one straight base plate edgeportion 313 adjacent to the concave edge portion 315.

In some examples, the concave edge portion 315 is centered along an edgeof the actuator 314. The actuator joint 317 also includes a gap 302between actuator 314 edge and the non-straight baseplate edge 311 toprovide enhanced stiffness, as shown in Table 2.

The dimension of the concave edge portion 315 is generally limited bymanufacturing factors, such as, for example actuator placementcapability, adhesive dispensing capability, etc. In manufacturingprocesses, the adhesive 316 can be first dispensed on the mountingshelves 318 before the actuator 114 is positioned and placed within theactuator joint 317.

TABLE 2 Gap Stroke (nm/V) Sway freq. (kHz)  50 um 12.4 21.6 100 um 11.420.8 Non-straight, 12.1 21.3 100 um max

Table 2 provides example gaps of varying dimensions, including thenon-straight baseplate edge, and the stroke and sway frequency of asuspension incorporating the gap dimensions. The concave edge portion315 can be located along the non-straight baseplate edge 311 to reducethe chance of adhesive 316 overflow.

The combination of straight and non-straight elements along thenon-straight baseplate edge 311 provides a better mechanical bond forthe adhesive 316 to the base plate 312. This, the straight andnon-straight elements are adhesive attach enhancement features. Thenon-straight elements allow for a larger cross section of the adhesive,leading to an improved internal strength of the adhesive. In specificexamples the adhesive's internal strength is improved at the concaveedge portion 315. The overall strength of the actuator joint 317 isincreased due to the increased adhesive's internal strength.

FIG. 5B illustrates the actuator joint 317 without the actuator, asillustrated in FIG. 5A. The adhesive along the straight elements of thenon-straight baseplate edge 311 protrudes from between the actuator andthe baseplate, with adhesive overflowing onto a bottom surface of theactuator when attached. While the adhesive overflow has traditionallybeen used to enable additional mechanical strength to the actuatorjoint, the adhesive overflow can short out the actuator 314 if theycontain conductive particles and extend up to the top conductivesurface.

Traditionally, more adhesive was desired to reduce the likelihood of anincomplete bond pad condition. As the adhesive volume is increased toensure a complete bond pad, the number of potentially rejected adhesiveoverflows is also increased. The reduced adhesive volume would cause anincrease in incomplete bond pads. The present disclosure allows for moretolerance in applying adhesive to ensure completed bond pads whilereducing adhesive overflows. Specifically, the non-straight baseplateedge is configured to receive an adhesive volume that would havepreviously been tolerable as adhesive overflow.

A maximum height tolerance of the adhesive overflow is specified forproduction of the disclosed components to achieve additional mechanicalstrength. The present disclosure allows for more tolerance in applyingadhesive to ensure the maximum height tolerance of the adhesive overflowisn't met for each component. The dimensions of the gap providesadditional mechanical strength that was previously achieved from theadhesive overflow.

The present disclosure seeks to reduce the instances of adhesiveoverflow in favor of the adhesive attach enhancement features disclosedherein. The additional strength enabled by the adhesive attachenhancement features counters the loss of strength seen from eliminatingor reducing the adhesive overflow.

FIG. 6 illustrates a first surface of a gimbal assembly 452 of asuspension 500, incorporating an example non-straight edge actuatorjoint 460. FIG. 7 is cross-sectional view of the actuator 414 area ofFIG. 6 taken along section line B-B′. Referring to FIG. 7, the actuator414 spans across a receiving area 605. An actuator 414 is illustratedwith a fixed end A and a hinge end B. Each end of the actuator 414 isbonded to the gimbal assembly 452 (of FIG. 6).

The actuator 414 includes a first electrode 701 on a top surface of theactuator 414, and a second electrode 702 on a bottom surface of theactuator 414. The hinge end B of the actuator 414 area includes a coverlayer 660, and a conductive layer 680 (e.g., copper), an insulatinglayer 690 (e.g., polyimide), and a metal base layer 650 (e.g.,stainless-steel). The second electrode 702 is electrically coupled tothe conductive layer 680 via a conductive adhesive 670. The metal baselayer 650 can be configured to incorporate a non-straightstainless-steel edge, for example the non-straight baseplate edge 311described with reference to FIG. 5A. The non-straight stainless-steeledge enables a gap 602. The gap 602 reduces the chance of electricalshorting between the conductive adhesive 670 and the metal base layer650. A non-conductive adhesive 630 is applied to fill the gap 602.

At the fixed end A, the first electrode 701 is electrically coupled tothe conductive layer 680 via a conductive adhesive 670. The top andbottom electrodes are separated at the fixed end A by the non-conductiveadhesive 630.

While multiple examples are disclosed, still other examples within thescope of the present disclosure will become apparent to those skilled inthe art from the detailed description provided herein, which shows anddescribes illustrative examples. Accordingly, the drawings and detaileddescription are to be regarded as illustrative in nature and notrestrictive. Features and modifications of the various examples arediscussed herein and shown in the drawings. While multiple examples aredisclosed, still other examples of the present disclosure will becomeapparent to those skilled in the art from the following detaileddescription, which shows and describes illustrative examples of thisdisclosure. Accordingly, the drawings and detailed description are to beregarded as illustrative in nature and not restrictive.

What is claimed is:
 1. A suspension comprising: a gimbal assemblyincluding: an actuator mounted on the suspension with a fixed end and ahinge end, opposite the fixed end, a first electrode on a top surface ofthe actuator, a second electrode on a bottom surface of the actuator,the second electrode is coupled to a conductive layer on the suspensionvia conductive adhesive, and a metal base layer located at the hingeend, the metal base layer includes a non-straight metal layer edgeconfigured to create a gap between an edge of the actuator and the metalbase layer; and the gap is configured to receive non-conductive adhesiveto prevent an electrical short between the conductive adhesive and themetal base layer.
 2. The suspension of claim 1, wherein the non-straightmetal layer edge of the metal base layer includes at least one straightbase plate edge portion.
 3. The suspension of claim 1, wherein thenon-straight metal layer edge of the metal base layer includes at leastone concave portion.
 4. The suspension of claim 1, wherein theconductive layer is a copper layer.
 5. The suspension of claim 1,wherein the metal base layer is stainless-steel.
 6. A gimbal assemblycomprising: an actuator mounted on a suspension device with a fixed endand a hinge end, opposite the fixed end; a first electrode on a topsurface of the actuator; a second electrode on a bottom surface of theactuator, the second electrode is coupled to a conductive layer on thesuspension device via conductive adhesive; a metal base layer located atthe hinge end, the metal base layer is configured to incorporate anon-straight metal layer edge to create a gap between an edge of theactuator and the metal base layer; and the gap is configured to receivenon-conductive adhesive to prevent an electrical short between theconductive adhesive and the metal base layer.
 7. The gimbal assembly ofclaim 6, wherein the non-straight metal layer edge of the metal baselayer comprises at least one straight base plate edge portion.
 8. Thegimbal assembly of claim 6, wherein the non-straight metal layer edge ofthe metal base layer comprises at least one concave portion.